The present invention relates to a differential gearing for vehicle comprising a plurality of pinion gears which are rotatably held within a differential case and a pair of side gears disposed in meshing engagement with the pinion gears and connected to left and right axles, respectively, and in particular, to a differential gearing for vehicle in which the pinion gears and the side gears are contained within a differential case of one-piece type.
A conventional differential gearing for vehicle is known as having a construction as disclosed in Japanese Registered Utility Model No. 2520728, for example. This differential gearing for vehicle of the prior art will be briefly described with reference to FIG. 11. It is to be noted that reference characters for the conventional construction shown in FIG. 11 will be indicated in parentheses in this specification. Formed in a differential case (12) are a pinion-gear-receiving opening (14) and an axle-receiving opening (16), which extend orthogonally to each other. Left and right side gears (20L, 20R) are disposed within the differential case (12) so as to be axially movable therein and are splined to left and right axles (22L, 22R), respectively, which are inserted into the axle receiving opening (16). Thrust washers (24) of a smaller diameter than the side gears (20L, 20R) are disposed between the back surface (20La, 20Ra) of the left and right side gears (20L, 20R) and the internal surface of the differential case (12).
Also disposed within the differential case (12) and rotatably supported therein is a pinion gear (26) having substantially the same external diameter as the internal diameter of the pinion gear-receiving opening (14). These pinion gears (26) are in meshing engagement with the left and right side gears (20L, 20R). A pinion gear holding plate (28) is fitted over the external diameter of the pinion gear (26), which is prevented from being removed from the differential case (12) by a snap ring (30), which is fitted into a groove (12a) in the differential case (12). A pinion shaft (32) is passed through the pinion gear (26) in alignment with the axis thereof to prevent its tilting.
To assemble the differential gearing for vehicle constructed in the manner mentioned above, the thrush washers (24) and the left and right side gears (20L, 20R) are assembled from the outside of the differential case (12) into the differential case (12) through the pinion gear receiving opening (14). The pinion gear (26) is then assembled into the pinion gear-receiving opening (14) from the outside of the differential case (12) in which the side gears (20L, 20R) have been assembled so as to mesh with the latter. At this time, the pinion shaft (32) is previously disposed within the differential case (12) so that the pinion gear (26) can be passed over the pinion shaft (32). After the pinion gear (26) has been assembled into the pinion gear receiving opening (14), the pinion gear holding plate (28) is fitted, which is then prevented from being removed by the snap ring (30).
With the construction according to the invention disclosed in the cited Utility Model, the side gears (20L, 20R) cannot be inserted into the differential case (12) after the pinion gear (26) is previously assembled. Accordingly, the side gears (20L, 20R) are initially assembled into the differential case (12), and then the pinion gear (26) is inserted through the pinion gear-receiving opening (14). As a consequence, to prevent a removal of the pinion gear (26) through the pinion gear receiving opening (14), there is a need to prevent a disengagement of the pinion gear (26) by fitting the pinion gear holding plate (28) around the outer periphery of the differential case (12). There is a problem that a construction in which the pinion gear holding plate (28), a separate member, used to prevent the disengagement of the pinion gear (26) leads to a reduced strength and an increased cost of the differential case (12).